1. Field
The present invention relates to a projector which projects colored images onto a screen or the like and, more particularly, to a projector-type image display apparatus which uses a color wheel to time-divide white light into respective color lights and modulates the color lights into image lights of respective colors by means of an image display device such as a DMD so as to project the image light onto a screen.
2. Description of the Related Art
There has recently been an increased demand for enjoying images on a large-sized screen more clearly and finely and, accordingly, demand for a projector and a private-use LCD television grows rapidly. Further, high-definition digital broadcasting has started to spread, accelerating needs for high-definition images and large-sized images.
Under such circumstance, a development race for a projector using various image display devices is underway, irrespective of whether its use is business or personal, for achieving a larger-sized and clearer screen.
A projection-type image display apparatus is available as one type of the projector, which uses a color wheel including red (R), green (G), and blue (B) filters (hereinafter referred to as “color segments”), to time-divide white light emitted from a light source into the respective color lights and modulates the color lights into image lights of the respective colors by means of an image display device such as a liquid crystal panel and a digital micromirror device (DMD) so as to project the image light onto a screen.
As a light source of such a projection type image display apparatus, a high-voltage discharge lamp capable of easily obtaining high brightness is typically used. However, discharge of the high-voltage discharge lamp may become unstable in some cases to make the brightness of the image on a screen unstable, degrading the image quality. Jpn. Pat. Appln. Publication No. 2004-212890 discloses a technique which superimposes a pulse current (hereinafter, referred to as a lamp pulse) on a discharge lamp drive current while a light emitted from a discharge lamp transmits through a white segment in order to prevent flickering of a high-voltage discharge lamp. The superimposition of the lamp pulse stabilizes the discharge of the high-voltage discharge lamp.
Further, Jpn. Pat. Appln. Publication No. 2002-49097 discloses a projection-type system which changes the strength of the drive current of a discharge current such that it achieves a maximum value when a specific (desirable) color is generated to control color balance. The drive current includes a lamp pulse for making the discharge of the discharge lamp stable and the duration of the lamp pulse corresponds to the length of time for generating a white color.
However, Jpn. Pat. Appln. Publication No. 2002-49097 does not refer to a concrete configuration or method that uses the lamp pulse for preventing flickering of the discharge lamp while a light emitted from a discharge lamp transmits through a color segment to easily control the color balance of a projected image.